The invention relates to a process for the intermediate sealing of the relevant upper waste layers of an operating dump and for the production of a multibarrier system to prevent seepage water penetrating into the body of the dump by means of intermediate covering of the dump layers.
An important task in the operation of dumps is to keep the amount of seepage water as small as possible. For this purpose, in the present state-of-the-art, waste is filled in layers having a height of, for example, 10 m and is covered with a layer of loam or other suitable material in a height of, for example 30 cm. The seepage waters obtained on these intermediate layers after further deposition are collected and treated.
On the basis of the state-of-the-art, the following requirements have now emerged with regard to the prevention or minimisation of seepage water in dumps:
By means of suitable technical measures, the entry of precipitation into the body of the dump should be minimised.
Precipitation should be kept away from the fill area by covering or sealing.
Fill areas which are neither covered nor sealed at the ends must have intermediate seals. Suitable materials for the intermediate seals are both the plastic web and cohesive earth material.
Plastic films which are laid in the form of roofing tiles, loosely or welded to one another, must be weighted down against gusts of wind. They must have high tensile strength and be weather-resistant.
The intermediate seal of cohesive material should have a minimum thickness of 20 cm after installation. The surface must be rolled smooth and protected from drying out or the effects of frost.
Before the fill areas with intermediate seals are put into operation again, the plastic films must be removed and the cohesive intermediate seals must be connected to the central seepage water disposal by additional measures.
According to the state-of-the-art described, the entry of precipitation into the dump and consequently the formation of seepage water can be reduced by intermediate seals of cohesive material.
A disadvantage of the mineral intermediate seal of cohesive material is its considerable volume, which is removed from the dump volume available for waste fill. Both for domestic waste and for commercial or industrial wastes and for special waste, the available dump volume is steadily becoming scarcer in all highly developed countries. This aspect is therefore becoming more and more important.
The penetration of precipitation into the waste layers of the dump and hence the formation of seepage water can be avoided by means of intermediate seals of plastic films. However, because of the regulation which prescribes that the plastic films have to be removed before the fill areas with intermediate seals are put into operation again, the intermediate covering films cannot be used as a permanent multibarrier system against seepage water. Consequently, precipitation which enters the surface of the waste if the intermediate covering made of plastic is damaged penetrates the entire body of the dump as far as the base. Furthermore, seepage waters released through dehumidification of higher waste layers penetrate the entire dump body underneath, as far as the base. Along this route through the body of the waste, further elution of the wastes and hence further enrichment of the seepage waters with pollutants must be expected.